1. Field of the Invention
The invention related to multiorifice structures and a method of fabrication and, more particularly, to a multiorifice structure spray disc for use in conjunction with an automotive type fuel injector valve for atomizing the fuel being injected into an internal combustion engine.
2. Prior Arts
The use of multiorifice structures in connection with nozzles for dispersing or atomizing an exiting fluid is well known in the art. Such multiorifice structures are found in a wide variety of applications ranging from old fashion sprinkling cans for watering a garden to sophisticated fuel injector valves for internal combustion engines. Whether the multiorifice structure merely disperses the fluid as with the sprinkling can or atomizes the fluid as in the fuel injector nozzle application depends upon several factors, one of which is the size of the apertures, as well as force with which the fluid is ejected. Atomization is best accomplished when fluid is ejected from relatively small apertures with relatively high forces. For automotive fuel injector applications, small apertures having effective diameters in the range from several hundred to less than one hundred microns appear to give the desired atomization without the need of having the fuel pressurized above tolerable limits. Unfortunately, multiorifice structures having apertures in ths size range are difficult to manufacture and their cost is prohibitive to meet the high volume, low cost needs for the automotive market.
Various techniques for making the desired multiorifice structure, such as drilling or punching, are impractical. Photoetching or chemical machining appear as a better approach but due to the depth of the apertures required, the desired uniformity of the apertures is difficult to achieve. Alternatively, the fusion of small diameter tubes disclosed by Roberts et al in U.S. Pat. No. 3,737,367 (June 1973) appears as the best approach taught by the prior art. The disadvantage of this approach is that the resultant aperture passages are parallel to each other and therefore the spray cone of the emitted fuel is limited. The divergence of the spray pattern emitted by the Roberts type structure can be increased by coining the structure to produce a curved surface. Alternatively, the parallel tubes in various sections of the structure may be angularly disposed as taught by Roberts et al in U.S. Pat. No. 3,713,202 (January 1973).
Atomization may also be obtained by twisting the individual rows of tubes, as taught by A. L. R. Ellis in U.S. Pat. No. 1,721,381 (June 1929). In this patent the alterante rows are twisted in the opposite direction to incease the turbulance thereby enhancing the mixing and combustion of the emitted gases. Ellis further teaches the use of the interstices between the tubes to pass the oxidizing gas which supports the combustion of the fuel gas passing through the tubes. E. E. Fassler in U.S. Pat. No. 3,602,620 (August 1971) teaches a thermal lance in which the oxidizing gas is fed to the tip of the lance through the interstices formed by twisting solid wires about a core. The twisted rods in this patent provide a tortuous path to impede the gas flow.